The present application relates to internal combustion engines, and, in particular, to cylinder crankcase assemblies.
Two-stroke, internal combustion engines usually are small (as opposed to 4-stroke engines) and therefore they are commonly used for lightweight vehicles such as motorcycles, mopeds or and motorized garden appliances such as trimmers, blowers, and chainsaws. Generally, it is desirable for these engines to be of a light weight.
The two-stroke engine generally is composed of a crankcase, cylinder block, and cylinder head, collectively referred to as a “cylinder crankcase short block.” Typically, a cylinder crankcase short block is made from separate components that need to be machined and fastened together, thus requiring mounting holes to be carefully machined within certain tolerances. Moreover, the fasteners add additional weight to the cylinder crankcase short block.
Cylinder crankcase short blocks also require seals between the components to avoid the leakage of air and/or fuel. The use of seals exposes the cylinder crankcase to failures such as the deterioration of a seal or leaking.
U.S. Pat. No. 2,489,150 to McCoy discloses an integrally cast cylinder crankcase and block. The cylinder head is a separate piece that must be mounted to the cylinder block so that a sleeve may be pressed into the cylinder block prior to the cylinder block being covered with the cylinder head. Similarly, U.S. Pat. No. 3,983,852 to Chatourel teaches a one-piece cylinder and crankcase with an integral cylinder head. The cylinder and crankcase casting of Chatourel, however, requires a separate cover that attaches to the casting. This cover “seals” the casting and acts as a support, or bearing surface, for a camshaft.